A former Army intelligence analyst and transgender woman, Manning was sentenced to 35 years in prison after being convicted in 2013 of stealing 750,000 pages of documents and videos before leaking them to WikiLeaks -- one of the largest and most embarrassing leaks of classified information in US history.

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But then-President Barack Obama commuted Manning's sentence in January, thereby providing her with an early release date.

Expressing relief about the impending release on Twitter Tuesday, Manning said: "Freedom was only a dream, and hard to imagine. Now it's here! You kept me alive <3"

Manning has been forced to serve her sentence in an all-male military prison despite a request to transfer to a civilian prison.

"For the first time, I can see a future for myself as Chelsea. I can imagine surviving and living as the person who I am and can finally be in the outside world," she said in a written statement. "I hope to take the lessons that I have learned, the love that I have been given, and the hope that I have to work toward making life better for others."

Manning's representatives could not provide her exact release date when reached by CNN, but a statement from the White House in January said her prison sentence is set to expire on May 17.

"Chelsea has already served the longest sentence of any whistleblower in the history of this country. It has been far too long, too severe, too draconian," Manning's attorneys, Nancy Hollander and Vincent Ward, said in a joint statement. "President Obama's act of commutation was the first time the military took care of this soldier who risked so much to disclose information that served the public interest."

News of Manning's commutation set off harsh criticism from some Republicans and intelligence officials who opposed the move in January, but Obama said she had served a "tough sentence."